Lecture 6 - OOP Concepts

Question 1

What concept encloses the data and functions that operate on that data into a single unit, the class?

Answer 1

Encapsulation

Question 2

TF: Hiding private details from the outside world is an example of encapsulation

Answer 2

True

Question 3

TF: Encapsulation allows external code to directly access class details without the use of predefined methods

Answer 3

False. They provide methods that allow users to access/modify it (i.e. no direct access)

Question 4

What concept separates interface of a class from its implementation and focuses on the interface?

Answer 4

Abstraction

Question 5

Hiding implementation details of a class and only presenting a clean and easy-to-use interface via class’ member function is an example of…

Answer 5

Abstraction

Question 6

What does isolating the impact of changes made to the code mean regarding Abstraction?

Answer 6

Means changes to internal implementation doesn’t affect how users/programs interact with the interface (i.e. changing internal implementation doesn’t affect how users/programs interact with it)

Question 7

What is meant by Black-box system in Abstraction?

Answer 7

System where internal workings or implementation details are hidden from the user (user can only interact with it through input, output)

Question 8

What is Inheritance in programming?

Answer 8

Concept where classes can be organized into hierarchies allowing code reuse

Question 9

What is polymorphism?

Answer 9

Ability of different classes (with same parent) to change the behaviour of the same method.
ex:
Parent class: Animal
Child classes: Dog, Cat
method in Animal, sound( ), changes bases on animal

Question 10

TF: A static method can use a non-static member

Answer 10

False. Static methods belong to class itself while non-static member belongs to instance of that class

Question 11

TF: Strongly typed languages means variables must be declared with a specific type and type conversions are explicit

Answer 11

True

Question 12

What is Singleton pattern?

Answer 12

Design pattern where only one instantiation of a class is allowed

Question 13

What are the three methods of implementing a Singleton pattern?

Answer 13

1. Eager Initialization method
2. Lazy Initialization method
3. Thread Safe Signleton method

Question 14

Which Singleton Pattern implementation method initializes the object at the time of class loading?

Answer 14

Eager Initialization method

Question 15

What is the advantage of Eager Initialization implementation of Singleton pattern?

Answer 15

Very simple to implement

Question 16

What are disadvantages of Eager Initialization implementation of Singleton pattern?

Answer 16

• Object is always instantiated even if it is never used (resource wastage, CPU time wastage)
• Cannot use Exception Handling

Question 17

Which Singleton Pattern implementation methods initializes the object only when it is requested? (2)

Answer 17

• Lazy Initialization method
• Thread Safe Singleton method

Question 18

What are the advantages of Lazy Initialization implementation of Singleton pattern?

Answer 18

• Creation takes place only when required
• Exception handling possible

Question 19

What is a disadvantage of Lazy Initialization implementation of Singleton pattern?

Answer 19

There is a need to check null condition each time

Question 20

Which Singleton Pattern implementation method uses synchronization to ensure the safe creation of a singleton instance in a multi-threaded environment?

Answer 20

Thread Safe Singleton Method

Question 21

What are the advantages of Thread Safe Singleton implementation of Singleton pattern? (2)

Answer 21

• Lazy initialization possible
• Thread-safe

Question 22

What is a disadvantage of Thread Safe Singleton implementation of Singleton pattern? (2)

Answer 22

getInstance( ) method synchronized which slows performance as it restricts simultaneous access to it by multiple threads